Hello, all. Hoping someone here could assist w/ issues concerning a 1970 Standel Studio Bass 30. Some background: amp powered up and functioned upon purchase 3 mos. ago w/ two JBL K130s (non original, but 8 ohms ea., wired parallel so showing 4 Ohms). Has original 2 prong cord. I swapped two 8 Ohm Madison branded 15" in (JBls went to another rig), and powered it up via a lamp limiter which was plugged into a Variac at 120v. Bottom speaker sounded out, but not top. After about 15 seconds, it sputtered, produced no sound, power light flickered & died. I looked up to see that the bulb was bright & shut it down. Then I discovered a potential culprit:
-The top speaker was not connected
I spoke w/ Danny McKinney, current owner of the Standel line, who is quite familiar w/ this amp and owns one himself. We sorted out that either:
A) Old caps finally gave way and it's coincidental that this occurred w/ speaker change
B) The unattached speaker wires toutched & fried output transistors
I got the chassis out & without measuring any values (which I don't know how to do- I have not progressed past basic safety, buying a variac, building a limiter and the ability to swap capacitors & upgrade to a 3 prong in an old Fender), I immediately saw a cap which appears shrunken & has white residue on it, which I'm hoping indicates that it has failed or is in the process of doing so, and that's the true culprit. It is teal blue & connected to two tabs directly behind the power indicator bulb (I'd include a pic but can't get one to upload). If I'm reading the schematic correctly (pdf link below), it's a C14 .02 600V. Can anyone ID this component as the death cap? If it is, can I simply snip it out, remove the two pronger, solder in the leads of a grounded cord, ground to chassis & test again?
Another clue is that someone, at some point, wrote "short PC" on the side of the chassis- maybe this problem was known by a previous owner?
That was a large amount of words to pose a short question. All thoughts & advice greatly appreciated.
http://www.standelamps.com/support/schematics/documents/1970/custandstudiobass_service.pdf
Be good,
-Pete
-The top speaker was not connected
I spoke w/ Danny McKinney, current owner of the Standel line, who is quite familiar w/ this amp and owns one himself. We sorted out that either:
A) Old caps finally gave way and it's coincidental that this occurred w/ speaker change
B) The unattached speaker wires toutched & fried output transistors
I got the chassis out & without measuring any values (which I don't know how to do- I have not progressed past basic safety, buying a variac, building a limiter and the ability to swap capacitors & upgrade to a 3 prong in an old Fender), I immediately saw a cap which appears shrunken & has white residue on it, which I'm hoping indicates that it has failed or is in the process of doing so, and that's the true culprit. It is teal blue & connected to two tabs directly behind the power indicator bulb (I'd include a pic but can't get one to upload). If I'm reading the schematic correctly (pdf link below), it's a C14 .02 600V. Can anyone ID this component as the death cap? If it is, can I simply snip it out, remove the two pronger, solder in the leads of a grounded cord, ground to chassis & test again?
Another clue is that someone, at some point, wrote "short PC" on the side of the chassis- maybe this problem was known by a previous owner?
That was a large amount of words to pose a short question. All thoughts & advice greatly appreciated.
http://www.standelamps.com/support/schematics/documents/1970/custandstudiobass_service.pdf
Be good,
-Pete